CN103364764B - Airborne radar non-stationary clutter suppression method - Google Patents

Abstract

The invention discloses an airborne radar non-stationary clutter suppression method, which comprises the following steps: firstly taking out echo data which is received by radar, is subjected to pulse compression, and belongs to a distance unit to be detected; estimating a space-time two-dimensional power spectrum by utilizing an iteration self-adaptive spectrum; reconstructing a covariance matrix by utilizing the space-time two-dimensional power spectrum, and revising the reconstructed covariance matrix; and finally calculating filtering weight by utilizing the revised covariance matrix, and carrying out clutter suppression in real time. With the adoption of the airborne radar non-stationary clutter suppression method, sample selection is not needed, and the problems of sample pollution and insufficient sample number can be effectively avoided; a whole space-time plane is considered when a clutter subspace is reconstructed, so that the airborne radar non-stationary clutter suppression method is more accurate, and is more excellent in clutter suppression; airspace subaperture smoothness is not needed, so that the problem of space-time aperture loss does not exist, and the method is not limited by an antenna structure; and with the adoption of a target rejection method, a notch is formed on an expectation objective on the space-time plane, so that the extra clutter suppression performance loss can be reduced; and the airborne radar non-stationary clutter suppression method can be used for airborne radar non-stationary clutter suppression.

Description

A kind of airborne radar non-stationary clutter suppression method

Technical field

The invention belongs to Radar Technology field, relate to airborne radar clutter suppression method, mainly based on the clutter suppression method of covariance matrix reconstruct, a kind of airborne radar non-stationary clutter suppression method specifically, for airborne radar non homogeneous clutter suppression.

Background technology

Airborne radar is with the characteristics of operation of its uniqueness, and being considered as by the military of various countries can the strategic weapon of left and right situation of battlefield, and clutter recognition performance be affect airborne radar can normally under look the principal element of work.First the space-time adaptive treatment S TAP technology proposed by Brennan and Reed effectively can suppress the land clutter be coupled during sky, and they propose a kind of STAP method simultaneously, and namely sample covariance matrix is inverted SMI method.Some distance sample that the method chooses contiguous unit to be detected carry out estimate covariance matrix, this is feasible under even clutter environment, but in fact, the distance of clutter spectrum is non-stationary, namely the space-time two-dimensional spectrum of clutter is along with distance change is (as non-working side battle array, double-basis, conformal array radar etc.) and clutter distribution heterogeneity, as landform, the spatial variations of landforms, man-made structures waits strong scattering point, high mountain blocks " shade " that cause and strong moving-target pollution etc., the statistical property of training sample can be caused to depart from the statistical property of the clutter of range unit to be detected, make the clutter recognition hydraulic performance decline of traditional STAP method, even can not meet the requirement that radar system normally works.

In order to solve the non-uniformity of clutter distribution, Melvin and Wicks proposes the screening sample method based on broad sense inner product, and the method needs the covariance matrix pre-estimating out unit to be detected, and this is difficult to realize in non-homogeneous clutter environment.The space-time adaptive treatment technology of the knowledge assistance occurred in recent years can improve the clutter recognition performance of airborne radar in non-homogeneous environment to a certain extent, but the priori obtained about clutter statistical characteristics needs to pay larger cost, such as need the cooperation of multiple sensors, and the accuracy requirement of this technology to priori is higher, implement cost very high, and this technology can make radar system become very complicated, and engineering not easily realizes.For the non-stationary problem of clutter, when without range ambiguity, solve clutter apart from non-stationary effective means by the compensation class methods that the noise track of the noise track of training sample and unit to be detected carries out registration, mainly with the Doppler effect correction method that the people such as Borsari propose, angle-Doppler effect correction method that the people such as Himed propose is representative.But these methods only consider the non-stationary problem of distance of clutter, do not consider the non-uniformity that clutter distributes, i.e. the problem such as non-homogeneous, the discrete clutter of power and target stains.In fact, the non-stationary heterogeneity distributed with clutter of clutter caused by observation geometry is simultaneous, this difficult problem that will traditional STAP algorithm caused under non-stationary environment simultaneously to face independent same distribution sample deficiency and sample contamination.In theory, the direct Data Domain Approach proposed by the people such as Sakar can solve clutter non-stationary that STAP faces and the non-uniformity that clutter distributes, but sub-aperture smoothing technique when the process employs sky, result in the loss in aperture during sky, and easily by the restriction of antenna structure, be only applicable to even linear array, in addition, the method pair array error and target directing error sensitive, in practical application, performance is not very desirable.

Summary of the invention

The object of the invention is to the problem for aperture loss when can not take into account clutter non-stationary and heterogeneity in above-mentioned prior art and exist empty simultaneously, propose a kind ofly to choose without the need to sample, without aperture loss time empty, by the airborne radar non-stationary clutter suppression method based on clutter covariance matrix reconstruct of antenna structure restriction, clutter recognition excellent performance.The clutter subspace of the present invention's reconstruct consider whole empty time plane, the clutter subspace of reconstruct is more accurate, more excellent to the rejection of clutter, in addition, target elimination method of the present invention only when sky in plane expectation target place formed recess, extra clutter recognition performance loss can be reduced.

Realizing technical scheme of the present invention is: utilize conventional iteration self-adapting Power estimation method to estimate the space-time two-dimensional power spectrum of unit to be detected, then avoid target to disappear mutually according to this Power spectrum reconstruction covariance matrix to covariance matrix correction, finally carry out clutter recognition with revised covariance matrix calculation of filtered weights.Its detailed process comprises as follows:

The echo data x of No. l range unit to be detected after pulse compression that step 1 takes out that radar receives _l, and utilize conventional iteration self-adapting Power estimation method to estimate the space-time two-dimensional spectral power matrix of this range unit l=1 ..., L, L are the number needing the range unit carrying out target detection;

Step 2 utilizes the space-time two-dimensional spectral power matrix estimating to obtain and steering vector matrix A reconstructs the space-time two-dimensional covariance matrix of l range unit and it is right revise, obtain revised covariance matrix

Step 3, under the prerequisite ensureing to expect that targeted signal gain is constant, according to linearly constrained minimum variance, utilizes revised covariance matrix calculate the space-time filtering device coefficient w of l range unit, kth Doppler's passage _{l, k}, k=1 ..., K, K are the number of Doppler's passage;

Step 4 utilizes the space-time filtering device w of kth Doppler's passage _{l, k}suppress data x _lin clutter, obtain the output z of l range unit, kth Doppler's passage _{l, k};

Step 5 makes k=k+1, repeats step (3) ~ (4), until all K Doppler's passage is disposed, exports the final doppler spectral after l range unit clutter recognition: z _l=[z _{l, 1}, z _{l, 2}..., z _{l, K}] ^t, wherein [] ^trepresent transposition;

Step 6 makes l=l+1, repeats step (1) ~ (5), until all L range unit is disposed, exports the spectrum of the range Doppler after L range unit clutter recognition Z=[z ₁, z ₂..., z _l] ^t.

Ground moving target detection looks one of main task of the onboard radar system of work under being, but under to be inevitably subject to the impact of land clutter depending on the onboard radar system of work, strong land clutter signal can flood the echoed signal of target, and influential system is to the detection of target.Therefore, effective Clutter Rejection Technique is needed depending on the onboard radar system of work under.The present invention just under look the technical scheme of this demand of the onboard radar system of work.First the present invention utilizes conventional iterative Adaptive spectra estimation method to estimate the space-time two-dimensional power spectrum of range unit to be detected, then the Power spectrum reconstruction utilizing estimation to obtain is without the covariance matrix of aperture loss during sky, then obtain not containing the covariance matrix of target component to the covariance matrix correction of reconstruct, finally carry out clutter recognition with revised covariance matrix calculation of filtered weights.

Realization of the present invention is also: wherein the space-time two-dimensional spectral power matrix that obtains is estimated in the utilization of step 2 and steering vector matrix A reconstructs the space-time two-dimensional covariance matrix of l range unit and it is right revise, obtain revised covariance matrix process, comprise the steps:

2a) first plane during whole sky is divided into K=K _sk _tindividual net point, K _sthe halved quantity of spatial frequency axle, K _tbe the halved quantity of Doppler frequency axle, the normalization spatial frequency that each point is corresponding and normalization Doppler frequency are respectively f _{s, n}, n=1,2 ..., K _sand f _{d, m}, m=1,2 ..., K _t, time empty, steering vector can be expressed as:

$s(f_{d,m},f_{s,n})={[1,e^{j2\mathrm{\π}{f}_{d,m}},...{,e}^{j2\mathrm{\π}{f}_{d,m}(M-1)}]}^T\⊗{[1,e^{j2\mathrm{\π}{f}_{s,n}},...{,e}^{j2\mathrm{\π}{f}_{s,n}(N-1)}]}^T$

Wherein M is umber of pulse, and N is spatial domain receiving cable number, [] ^trepresent transposition, represent that Kronecker amasss;

2b) utilize the space-time two-dimensional spectral power matrix estimating to obtain the space-time two-dimensional covariance matrix of l range unit is reconstructed with steering vector matrix A for:

Wherein $A=[s(f_{d,1},f_{s,1}),s(f_{d,2},f_{s,1}),...,s(f_{d,K_1},f_{s,K_s})]$ Steering vector matrix when representing MN × K dimension empty;

2c) when sky, plane finds and (f _dk, f _s0) nearest 4 net points, the coordinate of these 4 net points is designated as (f _di, f _si) (i=1 ..., 4), by power matrix the power of these 4 some correspondences can be determined, be designated as p _i(i=1 ..., 4), wherein f _s0for the normalization spatial frequency that radar main beam direction is corresponding;

2d) right revise as follows, obtain revised covariance matrix:

${\hat{R}}_{\mathrm{CN},l}={\hat{R}}_l-A_a{D}_a{A}_a^H$

Wherein D _a=diag{p ₁, p ₂, p ₃, p ₄, diag{} represents diagonal matrix, A _a=[s (f _d1, f _s1) ..., s (f _d4, f _s4)] be adjacent 4 steering vector matrixes formed.

STAP technology is utilized to suppress the clutter of range unit to be detected to need to estimate the covariance matrix of range unit clutter to be detected, when estimating that the covariance matrix obtained comprises echo signal, there will be echo signal to disappear mutually, this can cause target energy to be lost, and has a strong impact on the detection perform of system to target.Echo signal, by revising covariance matrix, is rejected by the present invention from clutter covariance matrix, and target can be avoided to disappear mutually, thus avoids target energy loss, is conducive to the detection of system to target.

The present invention compared with prior art has the following advantages:

1. traditional Doppler effect correction class methods do not take into account the non-stationary heterogeneity distributed with clutter of distance of clutter simultaneously, under non-homogeneous clutter environment, are faced with the problem of sample number deficiency and sample contamination; The present invention only make use of the data of unit to be detected, chooses without the need to sample, effectively avoids the problem of sample contamination and sample number deficiency.

2. the clutter subspace of the present invention's reconstruct consider whole empty time plane, the clutter subspace of reconstruct is more accurate, more excellent to the rejection of clutter, particularly evident at the clutter recognition performance improvement in sidelobe clutter district.

3. the present invention selects iteration self-adapting Power estimation method to estimate space-time two-dimensional power spectrum, can solve traditional direct Data Domain Approach exist empty time aperture loss problem; The present invention is level and smooth without the need to spatial domain sub-aperture, therefore not by the restriction of antenna structure.

4. target elimination method of the present invention only when sky in plane expectation target place formed recess, extra clutter recognition performance loss can be reduced.

Accompanying drawing explanation

Fig. 1 is airborne radar non homogeneous clutter suppression process flow diagram of the present invention;

Fig. 2 is space-time two-dimensional power spectrum chart of the present invention;

Fig. 3 is the improvement factor comparison diagram of the present invention and traditional direct Data Domain Approach;

Fig. 4 is the improvement factor comparison diagram of the present invention and Doppler shift method.

Embodiment

Below in conjunction with accompanying drawing, the present invention is described in detail:

Embodiment 1

The present invention is a kind of airborne radar non-stationary clutter suppression method based on clutter covariance matrix reconstruct, can be used for airborne radar non homogeneous clutter suppression.In this example, under radar is operated in forward-looking mode, radar emission signal is positioned at L-band, and wavelength is 0.2m, the distance samples frequency that radar adopts is 1MHz, pulse repetition rate is 400Hz, and radius of curvature of the earth is 6378km, and carrier aircraft height is 8km, carrier aircraft speed is 80m/s, pulse number is 22, and front antenna adopts comprehensive battle array of 1 × 11, and array element distance is 0.5 times of wavelength.Antenna axial direction and carrier aircraft velocity reversal angle are-90 °, and the angle of main beam pointing and antenna axial direction is 60 °, and the main beam angle of pitch is 0 °.Signal to noise ratio (S/N ratio) is 30dB, and miscellaneous noise ratio is 40dB.

Under these conditions, see Fig. 1, performing step of the present invention further describes as follows:

Step 1, radar receiver receives echoed signal, and radar signal processor carries out pulse compression to the echoed signal received, and takes out the echo data x of No. l range unit to be detected after pulse compression _l, and utilize conventional iteration self-adapting Power estimation method to estimate the space-time two-dimensional spectral power matrix of this range unit wherein l=1 ..., L, L are the number needing the range unit carrying out target detection.

(1.1) first plane during whole sky is divided into K=K _sk _tindividual net point, K _sthe halved quantity of spatial frequency axle, K _tbe the halved quantity of Doppler frequency axle, the normalization spatial frequency that each point is corresponding and normalization Doppler frequency are respectively f _{s, n}, n=1,2 ..., K _sand f _{d, m}, m=1,2 ..., K _t, time empty, steering vector can be expressed as:

$s(f_d,f_s)={[1,e^{j2\mathrm{\π}{f}_d},...{,e}^{j2\mathrm{\π}{f}_d(M-1)}]}^T\⊗{[1,e^{j2\mathrm{\π}{f}_s},...{,e}^{j2\mathrm{\π}{f}_s(N-1)}]}^T$

Wherein M is umber of pulse, and N is spatial domain receiving cable number, [] ^trepresent transposition, represent that Kronecker amasss.Initialization covariance matrix and establish iterations i=0 now.

(1.2) i-th iteration P is calculated _l ⁽ⁱ⁾in each element P _l ⁽ⁱ⁾the estimated value of (m, n):

${\hat{P}}_l^{\left(i\right)}(m,n)={\left|\frac{s^H(f_{d,m},f_{s,n}){\left({\hat{R}}_{m,n}\right)}^{-1}{x}_l}{s^H(f_{d,m},f_{s,n}){\left({\hat{R}}_{m,n}^{\left(i\right)}\right)}^{-1}s(f_{d,m},f_{s,n})}\right|}^2$

Wherein represent covariance matrix during i-th iteration.This is in the data that only make use of unit to be detected when estimating space-time two-dimensional spectral power matrix, chooses, make the present invention effectively can avoid the problem of sample contamination and sample number deficiency without the need to sample.

(1.3) when i >=1, judge whether i equals 10.When proposition is false, then calculate new covariance matrix:

${\hat{R}}_{m,n}^{(i+1)}=\underset{u=1,u\≠m}{\overset{K_1}{\mathrm{\Σ}}}\underset{v=1,v\≠n}{\overset{K_s}{\mathrm{\Σ}}}{\hat{P}}_l^{\left(i\right)}(u,v)s(f_{d,u},f_{s,v})s^H\left(f_{d,n}{,f}_{s,v}\right)$

And make i=i+1 turn back to (1.2) carrying out next iteration.When proposition is set up, then interrupt iterative process and also will as final output power estimated value, that is:

This step adopts iteration self-adapting Power estimation method to estimate space-time two-dimensional power spectrum, can solve that traditional direct Data Domain Approach exists empty time aperture loss problem, and due to level and smooth without the need to spatial domain sub-aperture, therefore not by the restriction of antenna structure.

Step 2, utilizes the space-time two-dimensional spectral power matrix estimating to obtain and steering vector matrix A reconstructs the space-time two-dimensional covariance matrix of l range unit and it is right revise, obtain the covariance matrix of revised l range unit

(2.1) the space-time two-dimensional spectral power matrix estimating to obtain is utilized the space-time two-dimensional covariance matrix of l range unit is reconstructed with steering vector matrix A for

Wherein $A=[s(f_{d,1},f_{s,1}),s(f_{d,2},f_{s,1}),...,s(f_{d,K_1},f_{s,K_s})]$ Steering vector matrix when representing MN × K dimension empty.This step consider when reconstructing clutter subspace whole empty time plane, the clutter subspace of reconstruct is more accurate, more excellent to the rejection of clutter, particularly evident at the clutter recognition performance improvement in sidelobe clutter district.

(2.2) when sky, plane finds and (f _dk, f _s0) nearest 4 net points, the coordinate of these 4 net points is designated as (f _di, f _si) (i=1 ..., 4), by power matrix the power of these 4 some correspondences can be determined, be designated as p _i(i=1 ..., 4), wherein f _s0for the normalization spatial frequency that radar main beam direction is corresponding.

(2.3) right revise as follows, obtain revised covariance matrix:

${\hat{R}}_{\mathrm{CN},l}={\hat{R}}_l-A_a{D}_a{A}_a^H$

Wherein D _a=diag{p ₁, p ₂, p ₃, p ₄, diag{} represents diagonal matrix, A _a=[s (f _d1, f _s1) ..., s (f _d4, f _s4)] be adjacent 4 steering vector matrixes formed., by revising covariance matrix, echo signal being rejected from clutter covariance matrix herein, target can be avoided to disappear mutually, thus avoid target energy loss, be conducive to the detection of system to target.

Step 3, supposes that this range unit exists target, under the prerequisite ensureing to expect that targeted signal gain is constant, according to linearly constrained minimum variance, utilizes revised covariance matrix calculate the space-time filtering device coefficient of l range unit, kth Doppler's passage:

$w_{l,k}=\frac{{\hat{R}}_{\mathrm{CN},l}^{-1}s(f_{\mathrm{dk}},f_{s0})}{s^H(f_{\mathrm{dk}},f_{s0}){\hat{R}}_{\mathrm{CN},l}^{-1}s(f_{\mathrm{dk}},f_{s0})}$

Wherein, s (f _dk, f _s0) for expecting echo signal corresponding empty time steering vector, [] ^hrepresent conjugate transpose, k=1 ..., K, K are the number of Doppler's passage.In above formula, the expression formula of denominator is because the present invention adopts linearly constrained minimum variance under the prerequisite ensureing to expect that targeted signal gain is constant, therefore denominator is a constant when expectation target signal gain is constant, and this is conducive to the design of space-time filtering device.

Step 4, utilizes the space-time filtering device w of kth Doppler's passage _{l, k}suppress data x _lin clutter, obtain l range unit, the output of kth Doppler's passage be:

Step 5, makes k=k+1, repeats step (3) ~ (4), until all K Doppler's passage is disposed, exports the final doppler spectral after l range unit clutter recognition: z _l=[z _{l, 1}, z _{l, 2}..., z _{l, K}] ^t.

Step 6, makes l=l+1, repeats step (1) ~ (5), until all L range unit is disposed, exports the final range Doppler spectrum Z=[z after L range unit clutter recognition ₁, z ₂..., z _l] ^t.According to the range Doppler spectrum Z obtained, what radar system was real-time carries out the work such as moving object detection, moving target parameter estimation and motion estimate.

Advantage of the present invention further illustrates by following emulation experiment.

Embodiment 2

A kind of airborne radar non-stationary clutter suppression method, with embodiment 1, is further detailed below by the performance of emulation experiment to clutter suppression method of the present invention.

1. simulation parameter

Non-stationary clutter when the clutter of Air-borne Forward-looking battle array radar is typical sky, therefore adopt Air-borne Forward-looking battle array radar in emulation.In this experiment, the distance samples frequency B that radar adopts is 1MHz, and wavelength X is 0.2m, pulse repetition rate f _rfor 400Hz, radius of curvature of the earth R is 6378km, and carrier aircraft height H is 8km, carrier aircraft speed V is 80m/s, and pulse number P is 22, and front antenna adopts comprehensive battle array of 1 × 11, array element distance is 0.5 times of wavelength, and meet d/ λ≤0.5, antenna radiation pattern there will not be graing lobe.Miscellaneous noise ratio CNR is 40dB, and antenna axial direction and carrier aircraft velocity reversal angle α are-90 °, and the angle ψ of main beam pointing and antenna axial direction is 60 °, the main beam angle of pitch it is 0 °.Process for No. 334 range units (50.1km).Near unit to be checked, No. 339 range gate has a moving-target, and its normalized Doppler frequency is 0.3, and signal to noise ratio (S/N ratio) is 20dB.

2. emulated data result and analysis

A. first this experiment emulates space-time two-dimensional power spectrum of the present invention, simulation result as shown in Figure 2, wherein, horizontal ordinate represents normalization Doppler frequency, ordinate represents normalization spatial domain frequency, and the amplitude in figure represents power, and unit is dB, color represents that power is larger more in vain, and color more black expression power is less.As can be seen from Figure 2, the space-time two-dimensional spectrum that the present invention estimates can react the Spectral structure characteristic of unit to be detected comparatively really, utilizes it to carry out clutter recognition and can obtain good effect.

B., in order to further illustrate superiority of the present invention, when the array element amplitude phase error of existence 3%, the improvement factor of other two kinds of methods and improvement factor comparing result of the present invention is given.Fig. 3 is traditional direct Data Domain Approach and improvement factor comparing result figure of the present invention.As can see from Figure 3, clutter recognition performance of the present invention will obviously be better than traditional direct Data Domain Approach, and this is because the present invention does not lose aperture when reconstructing covariance matrix.Fig. 4 is the improvement factor comparing result figure of the present invention and Doppler shift method.As we can see from the figure, the present invention is all better than Doppler shift penalty method in the clutter recognition performance in main-lobe clutter district and sidelobe clutter district, this be due to the present invention consider when covariance matrix reconstructs whole empty time plane, the clutter subspace of reconstruct is more close to real clutter subspace.Can also see from Fig. 4, the present invention does not form recess at No. 52 Doppler's passage, and this is because the present invention only make use of the data of unit to be detected itself, adjacency door whether passive target pollution on the rejection of clutter without impact.

To sum up, a kind of airborne radar non-stationary clutter suppression method based on clutter covariance matrix reconstruct that the present invention proposes, mainly solves in prior art the problem of aperture loss when can not take into account clutter non-stationary and heterogeneity simultaneously and exist empty.The present invention only make use of the data of unit to be detected, chooses without the need to sample, effectively avoids sample contamination and the not enough problem led of sample number; The clutter subspace of the present invention's reconstruct consider whole empty time plane, the clutter subspace of reconstruct is more accurate, more excellent to the rejection of clutter.The present invention is level and smooth without the need to spatial domain sub-aperture, therefore not by the restriction of antenna structure, and without aperture loss during sky, in addition, target elimination method of the present invention only when sky in plane expectation target place form recess, extra clutter recognition performance loss can be reduced.

Claims (1)

1. an airborne radar non-stationary clutter suppression method, is characterized in that: comprise the steps:

The echo data x of No. l range unit to be detected after pulse compression that step 1 takes out that radar receives _l, and utilize conventional iteration self-adapting Power estimation method to estimate the space-time two-dimensional spectral power matrix of this range unit wherein l=1 ..., L, L are the number needing the range unit carrying out target detection;

Step 2 utilizes the space-time two-dimensional spectral power matrix estimating to obtain and steering vector matrix A reconstructs the space-time two-dimensional covariance matrix of l range unit and it is right revise, obtain revised covariance matrix comprise the steps:

2a) first plane during whole sky is divided into K=K _sk _tindividual net point, K _sthe halved quantity of spatial frequency axle, K _tbe the halved quantity of Doppler frequency axle, the normalization spatial frequency that each point is corresponding and normalization Doppler frequency are respectively f _{s, n}, n=1,2 ..., K _sand f _{d, m}, m=1,2 ..., K _t, time empty, steering vector is expressed as:

$s(f_{d,m},f_{s,n})={[1,e^{j2\mathrm{\π}{f}_{d,m}},...,e^{j2\mathrm{\π}{f}_{d,m}(M-1)}]}^T{\⊗[1,e^{j2\mathrm{\π}{f}_{s,n}},...,e^{j2\mathrm{\π}{f}_{s,n}(N-1)}]}^T$

Wherein M is umber of pulse, and N is spatial domain receiving cable number, [] ^trepresent transposition, represent that Kronecker amasss;

2b) utilize the space-time two-dimensional spectral power matrix estimating to obtain the space-time two-dimensional covariance matrix of l range unit is reconstructed with steering vector matrix A for:

Wherein $A=[s(f_{d,1},f_{s,1}),s(f_{d,2},f_{s,1}),...,s(f_{d,K_t},f_{s,K_s})]$ Steering vector matrix when representing MN × K dimension empty;

2c) when sky, plane finds and (f _dk, f _s0) nearest 4 net points, the coordinate of these 4 net points is designated as (f _di, f _si) (i=1 ..., 4), by power matrix determine the power of these 4 some correspondences, be designated as p _i(i=1 ..., 4), wherein f _s0for the normalization spatial frequency that radar main beam direction is corresponding;

2d) right revise as follows, obtain revised covariance matrix:

${\hat{R}}_{\mathrm{CN},l}={\hat{R}}_l-A_a{D}_a{A}_a^H$

Wherein D _a=diag{p ₁, p ₂, p ₃, p ₄, diag{} represents diagonal matrix, A _a=[s (f _d1, f _s1) ..., s (f _d4, f _s4)] be adjacent 4 steering vector matrixes formed;

Step 3, under the prerequisite ensureing to expect that targeted signal gain is constant, according to linearly constrained minimum variance, utilizes revised covariance matrix calculate the space-time filtering device coefficient w of l range unit, kth Doppler's passage _{l, k}, k=1 ..., K, K are the number of Doppler's passage;

Step 4 utilizes the space-time filtering device w of kth Doppler's passage _{l, k}suppress data x _lin clutter, obtain the output z of l range unit, kth Doppler's passage _{l, k};

Step 5 makes k=k+1, repeats step (3) ~ (4), until all K Doppler's passage is disposed, exports the final doppler spectral after l range unit clutter recognition: z _l=[z _{l, 1}, z _{l, 2}..., z _{l, K}] ^t, wherein [] ^trepresent transposition;

Step 6 makes l=l+1, repeats step (1) ~ (5), until all L range unit is disposed, exports the spectrum of the range Doppler after L range unit clutter recognition Z=[z ₁, z ₂..., z _l] ^t.